Closes #875

Closes #754

Not linked yet. Beta comes out later this week.

Since these no longer follow directly from scroller.clientHeight/Width.

Use these to ensure messages for current line are scrolled into view
in demo/widget.html.

Closes #802

Huge refactor of lib/codemirror.js. Most code is now top-level (in the
module wrapper function) rather than inside of the CodeMirror
constructor sharing a huge amount of state.

A CodeMirror instance now has (non-public) `display`, `view`, and
`options` properties that describe its state. The display holds the
editor's DOM structure and associated state, view represents a view on
a document, containing `doc`, `sel`, `overwrite`, `scrollTop`, and
`scrollLeft` properties. The `doc` itself contains its history.

(It is not yet possible to switch views and documents in and out of an
editor, but this does start clearing the way towards that.)

This makes the formatter easier to adjust to new mode, and
cleans it up somewhat.

And move closetag over to it.

This makes the code that gets the XML state out of the mode actually
sound and extensible.

Issue #820

Closes #819

Cleans up the implementation of marked ranges, makes the data
structure for markers-within-a-line persistant, and attaches them to
the lines stored in the undo history when necessary.

Closes #675

This was especially noticeable with non-default font-sizes. The wrapper div and additional pre are required due to using the font-size provided by the browser (using em throughout).

Instead of a single 'inline' option, add noHScroll and coverGutter options.

Closes #781

The off pun is rather awful, but it does have precedent, and is
more succinct.

 - Background parsing now never goes past the visible part of the
   document.

 - We only store style information for lines that are actually visible
   (and then keep it cached).

 - When the document changes, background highlighting always
   re-highlights from the change to the end of the visible part.

 - Gets rid of compareState mode methods and the hairy heuristic that
   tried to simulate it when absent.

 - The onHighlightComplete callback was removed, since it no longer
   really applies -- the document is only fully parsed when scrolled
   to its end.

This should help preserve memory (a huge document will no longer
immediately have parser state and highlighting information built up
for all lines, but only for the parts that you look at), and removes
the pathological case when you, for example, are typing at the top of
a huge XML document, and opening or closing a tag causes a whole
re-highlight to cascade all the way to the bottom because the
compareState will detect a change.

Issue #688

Fixes a problem where the editor would always be 30 pixels smaller
than its set height.

The height is now set on the outer wrapper DIV again, and some
height: 100% tricks are used to make height information flow
both ways (inside-out in demo/resize.html mode, outside-in in
normal, fixed-height mode).

Closes #775

Add CodeMirror.defineOption function for defining new options.

Add findMatchingBracket to the methods exported by this extension.

Closes #746

It is now more structured (knows about ranges) and allows automatic
unfolding when the cursor enters the folded range.

This allows multiple handlers to listen for a single event, and makes
the API a bit more uniform.

Issue #725

Issue #294

No more random {x,y,yBot} thrown into the mix.

- Multiple gutters are explicitly created with the gutters
  option
- Markers go into a specific gutter, new setGutterMarker,
  clearGutter methods
- The line number gutter is separate
- The 'fixedGutter' feature is removed (painful to do now,
  was shaky anyway)

(codemirror2 -> codemirror)

String.prototype.charAt returns '' (empty string) for characters outside the range of the string.